This application is based on Japanese Patent Application Nos. 2001-188516 filed Jun. 21, 2001, 2001-243318 filed Aug. 10, 2001, and 2002-176341 filed Jun. 17, 2002, the contents of which are incorporated hereinto by reference.
1. Field of the Invention
The present invention relates to an ink-jet printing head and an ink-jet printing apparatus and method.
2. Description of the Related Art
Ink-jet printing apparatuses, which eject ink droplets from an ink-jet printing head to print an image, can print an image with various gradations by varying the size of the droplets.
A conventional ink-jet printing head, for example, the one described in U.S. Pat. No. 5,208,605, has two nozzle lines formed therein parallel with each other and extending in a direction crossing a scanning direction. One of the nozzle lines has a plurality of larger-diameter nozzles (larger-diameter ejection openings) arranged at equal intervals and through which a large ink droplets are ejected. In contrast, the other nozzle line has a plurality of smaller-diameter nozzles (smaller-diameter ejection openings) arranged at equal intervals and through which a small ink droplets are ejected.
A printing head constructed in this manner ejects ink droplets through the larger- and smaller-diameter nozzles while moving in the scanning direction, to form large and small ink dots on a printing medium.
Typically, the ink-jet printing head executes a recovery process of discharging ink that does not contributes to image printing, through the nozzles in order to maintain the appropriate ink ejection performance. The recovery process includes, for example, a suction recovery process of sucking and discharging ink through the nozzles and a pressurization recovery process of pressurizing the interior of the printing head to discharge the ink through the nozzles. Ink is supplied to each nozzle through a corresponding ink channel, and also during the recovery process, ink supplied through the respective ink channels is discharged.
However, in the above described conventional ink-jet printing head, one of the nozzle lines (larger-diameter nozzle line) has only the plurality of larger-diameter nozzles arranged therein and having a smaller ink flow resistance, whereas the other nozzle line (smaller-diameter nozzle line) has only the plurality of smaller-diameter nozzles arranged therein and having a larger ink flow resistance. Consequently, the recovery process has the following problems: If the recovery process is simultaneously executed on the plurality of larger-diameter nozzles and the plurality of smaller-diameter nozzles, a large ink flow occurs through the larger-diameter nozzle, whereas an ink flow is unlikely to occur in the smaller-diameter nozzle line. It is thus difficult to sufficiently discharge ink through the smaller-diameter nozzles. Accordingly, the ink channels that are in communication with the smaller-diameter nozzles cannot be filled with ink. As a result, the recovery process may be insufficient for the smaller-diameter nozzles. The recovery process is likely to be particularly insufficient for the smaller-diameter nozzles if the ink channels that are in communication with the plurality of larger-diameter nozzles are connected to one side of a common ink supply passage, while the ink channels that are in communication with the plurality of smaller-diameter nozzles are connected to the other side of the common ink supply passage. That is, there occurs a large difference in ink flow between the one and other sides of the common ink supply passage, further hindering ink from being discharged through the smaller-diameter nozzles.
It is an object of the present invention to provide an ink-jet printing head and an ink-jet printing apparatus and method which enable not only larger-diameter nozzles but also smaller-diameter nozzles to be sufficiently recovered.
In a first aspect of the present invention, there is provided an ink-jet printing head comprising:
a plurality of nozzles through which ink is ejected;
a plurality of ejection energy generating members provided in correspondence with the plurality of nozzles to generate ejection energy used to eject ink through the plurality of nozzles;
a plurality of ink channels which are in communication with the plurality of nozzles and which are provided with the plurality of ejection energy generating members; and
an ink supply port through which ink is supplied to the plurality of ink channels, wherein
the plurality of nozzles include larger-diameter nozzles and smaller-diameter nozzles, the number of smaller-diameter nozzles being larger than that of larger-diameter nozzles,
the plurality of ink channels include first ink channels in communication with the larger-diameter nozzles and second ink channels in communication with the smaller-diameter nozzles, and
the first ink channels and the second ink channels are mixed and arranged along the ink supply port so that a group of smaller-diameter nozzles composed of a plurality of the smaller-diameter nozzles is arranged between the lager-diameter nozzles.
In a second aspect of the present invention, there is provided an ink-jet printing method for printing on a printing medium using an ink-jet printing head of the present invention, wherein
the printing medium is printed using ink droplets ejected through the larger-diameter nozzles and through the smaller-diameter nozzles.
In a third aspect of the present invention, there is provided an ink-jet printing apparatus for printing on a printing medium using an ink-jet printing head of the present invention, comprising:
movement means for the ink-jet printing head and the printing medium relatively to each other, and
wherein ink droplets ejected through the larger-diameter nozzles and through the smaller-diameter nozzles are allowed to impact the printing medium.
In the ink-jet printing head according to the present invention, the number of larger-diameter nozzles is larger than that of smaller-diameter nozzles, the ink channels in communication with the larger-diameter nozzles and the ink channels in communication with the smaller-diameter nozzles are arranged with mixing each other along the ink supply port, and a group composed of plurality of smaller-diameter nozzles is arranged between the larger-diameter nozzles. Thus, during a process of discharging ink through the nozzles, a relatively large ink flow occurs which moves from the ink supply port to the larger-diameter nozzle. Accordingly, the ink flows more easily to the plurality of smaller-diameter nozzles, located between the larger-diameter nozzles. As a result, a sufficient recovery process can be executed on the smaller-diameter nozzles too.
Further, since the number of the smaller-diameter nozzles is larger than that of the larger-diameter nozzles, more small dots can be used to print an image with a higher definition. Furthermore, the use frequency of the smaller-diameter nozzles can be distributed to improve their durability.
Moreover, by setting the arrangement of the larger- and smaller-diameter nozzles on the basis of the relationship between the ink channels and ejection speed of the droplets, an excellent recovery process can be executed on the smaller-diameter nozzles while maintaining the appropriate image printing performance. Further, a higher-quality image can be printed by combining large and small dots, formed using the larger- and smaller-diameter nozzle, in various manners depending on the arrangement of the larger- and smaller-diameter nozzles.
The above and other objects, effects, features and advantages of the present invention will become more apparent from the following description of embodiments thereof taken in conjunction with the accompanying drawings.